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1. Field of the Invention
The present invention relates to the salvage or installation of marine platforms and oil rigs that are supported upon a usually partially submerged jacket that extends between the seabed and the water surface. Even more particularly, the present invention relates to the use of a moving lifting assembly which is preferably barge supported that can remove and salvage or install very large marine platforms without the use of enormous lifting booms such as form a part of derrick barges, offshore cranes, and the like. The present invention features opposed short booms that are connected with an improved lifting arrangement to the lower end of the platform to be salvaged or installed.
2. General Background
In the offshore oil and gas industry, the search for oil and gas is often conducted in a marine environment. Sometimes the search takes place many miles offshore. Oil and gas well drilling takes place in many hundreds of feet of water depth.
The problem of drilling oil wells offshore and then producing these wells has been solved in part by the use of enormous fixed or floating platform structures with foundations that are mostly submerged, but usually extending a number of feet above the water surface. Upon this foundation (or xe2x80x9cjacketxe2x80x9d, tension leg platform (xe2x80x9cTLPxe2x80x9d), or SPAR, etc. referred to in the art) there is usually placed a very large prefabricated rig, deck, or platform.
The term xe2x80x9cplatformxe2x80x9d as used herein should be understood to include any of a large variety of prefabricated structures that are placed in a marine environment, e.g., on an offshore foundation (e.g. jacket), to form a fixed or floating offshore platform. Thus, a xe2x80x9cplatformxe2x80x9d can include, e.g. a drilling rig, a production platform, a crew quarters, living quarters, or the like.
A supporting jacket is usually a very large multi-chord base formed of multiple sections of structural tubing or pipe that are welded together. Such jackets have been used for a number of years for the purpose of supporting large deck platforms in an offshore environment.
The jacket or foundation is usually prefabricated on land in a fabrication yard, preferably adjacent to a navigable waterway. The completed jacket can be placed upon a large transport barge so that it can be moved to the drill site where it will be placed upon the ocean floor. As an example, an offshore jacket can be several hundred feet in length. The size of the jacket is of course a function of the depth of water in which the rig will be placed. A five hundred (500) foot water depth at the drill site (or production site) will require a jacket which is approximately 500-550 feet tall. The jacket is usually partially submerged, with only a small upper portion of the jacket extending slightly above the water surface. An offshore jacket as described and in its position on the seabed can be seen, for example, in the Blight, et al U.S. Patent No. 4,252,469 entitled xe2x80x9cMethod and Apparatus for installing integrated Deck Structure and Rapidly Separating Same from Supporting Barge Means.xe2x80x9d Specifically, FIGS. 1, 2 and 3 of the Blight, et al patent show an offshore jacket on the seabed.
A small upper portion of the jacket extends above the water surface. This exposed portion of the jacket is the portion upon which the platform is placed and supported by. The upper portion of the jacket is usually equipped with a number of alignment devices which enhance the proper placement of the deck package on the jacket. Such alignment devices are referred to variously as stabbing eyes, sockets, or the like. The use of such alignment devices, sockets, or stabbing eyes can be seen in the Blight, et al U.S. Pat. Nos. 4,252,468 and U.S. Pat. No. 4,252,469 as well as in the Kansan U.S. Pat. No. 4,242,011. For purposes of background and reference, the Kansan patent U.S. Pat. No. 4,242,011 is incorporated herein by reference. The Blight, et al U.S. Pat. Nos. 4,252,469 and 4,252,468 are likewise each incorporated herein by reference.
Platforms or topsides can be extremely large and have correspondingly heavy weights. For example, it is not uncommon for a deck platform such as a drilling rig crew quarters, production platform or the like to be between five hundred and five thousand (500 and 5,000) tons gross weight. Topsides in excess of ten thousand (10,000) tons have been installed, and others that are being planned may weigh as much as thirty thousand (30,000) tons. Such enormous load values present significant problems in the placement of deck platforms on offshore jacket structures. First, the placement is done entirely in a marine environment. While the jacket can be laid on its side and/or floated into position, the platform is not a submersible structure, and must be generally supported in an upright condition above the water surface to prevent water damage to the many components that form a part of the drilling or production platform (such as electrical systems, wall constructions, and other portions that will be inhabited by individuals and used as oil and gas well drilling or production equipment).
After a number of years, offshore marine platforms can become obsolete and are abandoned. Once abandoned, these platforms become a hazard to navigation and must necessarily be removed.
The art has typically used enormous derrick barges for the purpose of removing abandoned platforms from their supporting jackets in an offshore environment. These derrick barges are large, rectangular barge structures with a high capacity lifting boom mounted at one end portion of the deck of the barge. The barge, for example might be three hundred to four hundred (300-400) feet in length, fifty to one hundred twenty (50-120) feet in width, and twenty-five to fifty (25-50) feet deep. These figures are exemplary.
A derrick barge might have a lifting capacity of for example, two thousand (2,000) tons. For very large structures such as for example, a five thousand (5,000) ton deck package, two derrick barges can be used, each supporting one side portion of the deck platform with a multi-line lift system supported by an enormous structural boom extending high into the air above the package during the lift.
While the use of such derrick barges has been successful in the removal of platforms and/or jackets through the years, such derrick barges are generally limited in their capacity to packages of two thousand (2,000) tons or less. Further, derrick barges of such an enormous capacity are extremely expensive to manufacture and operate. Many thousand of dollars per hour as a cost of using such a device is not uncommon. Although there are five (5) or six (6) derrick barges that can lift in excess of six thousand (6,000) tons, they are extremely costly and limited as to the water depth in which they can operate.
When very large loads of, for example six thousandxe2x80x94ten thousand (6,000-10,000) tons are involved, the limitation of the derrick barge usually prohibits such a lift.
In U.S. Pat. No. 4,714,382 issued to Jon Khachaturian there is disclosed a method and apparatus for the offshore installation of multi-ton prefabricated deck packages on partially submerged jacket foundations. The Khachaturian patent uses a variable dimensional truss assembly and is supported by the barge and forms a load transfer interface between the barge and the deck package. Upper and lower connections form attachments between the truss members and the deck package at upper and lower elevational positions on the deck package. The variable dimension truss includes at least one member of variable length, in the preferred embodiment being a winch powered cable that can be extended and retracted by winding and unwinding the winch. Alternate embodiments include the use of a hydraulic cylinder as an example. Other Khachaturian patents include U.S. Pat. Nos. 5,607,260; 5,609,441; 5,662,434; 5,800,093; and 5,975,807; each of which is hereby incorporated herein by reference.
An earlier patent, U.S. Pat. No. 2,598,088 issued to H. A. Wilson entitled xe2x80x9cOffshore Platform Structure and Method of Erecting Samexe2x80x9d discusses the placement of drilling structure with a barge wherein the legs of the drilling structure are placed while the drilling structure is supported by two barges. The Wilson device does note use truss-like lifting assemblies having variable length portions which are placed generally on opposite sides of the deck package. Rather, Wilson relates to a platform which is floated in place and the support legs are then placed under the floating platform. Thus, in the Wilson reference, an in-place underlying supporting jacket is not contemplated.
The Natvig, et al U.S. Pat. No. 3,977,346 discusses a method of placing a deck structure upon a building site such as a pier. The method includes the pre-assembly of a deck structure upon a base structure on land so that the deck structure extends outwardly over a body of water. Floating barges are provided for supporting the deck structure outwardly of the building site. The deck structure is then transferred to the supportive base structure by means of barges. The Natvig reference uses two barges which are placed on opposite sides of a platform with pedestal type fixed supports forming a load transfer member between the barges and the platform. However, the fixed pedestal of Natvig is unlike the truss-like lifting arrangement of applicant which include movable portions at least one of which can be of a variable length.
U.S. Pat. No. 4,249,618, issued to Jacques E. Lamy, discloses a method of working an underwater deposit comprising the following stages: a) constructing and positioning a platform structure, equipped before or after positioning with drilling devices and installations, b) executing drilling using these devices and installations, c) constructing and equipping, during stages a) and b), a production bridge fitted with devices and installations required for production, d) transporting the production bridge to, and positioning it on, said platform structure, and e) commencing production from deposit. The drilling bridge may remain in position on the platform structure during stages d) and e) or it may be removed to make way for the production bridge.
U.S. Pat. No. 4,744,697, issued to Anton Coppens, discloses a vessel that is provided for installing or removing a module on or from a support structure erected in a body of water. The vessel is able to suspend the module over the support structure by cranes enabling installation or removal of the module to be accomplished while the module is being suspended.
U.S. Pat. No. 5,037,241, issued to Stephen D. Vaughn et al. discloses an improved apparatus for setting a deck structure or other marine superstructure using a barge mounted cantilevered support structure. The cantilevered support structure is attached at one end of a floating vessel. The cantilevered support structure extends past the edge of the vessel and, in one embodiment, includes means for rotating parallel support members about the deck of the floating vessel permitting the cantilevered support structure to be raised and lowered while it remains substantially parallel with the top of the offshore platform enabling the superstructure to engage the top of a previously installed offshore platform in a synchronized manner. Alternatively, this superstructure may be aligned directly over the platform. A cantilevered drilling rig is then aligned over the cantilevered support structure and used to lift the deck structure or marine superstructure, permitting the vessel and cantilevered support structure to move. The drilling rig is then used to lower the marine superstructure onto the top of the previously installed offshore platform.
The present invention provides a catamaran work barge apparatus for lifting and removing a marine platform to be salvaged or installed. The apparatus includes a pair of barges, each providing a deck area with a base that can support a large multi-ton load.
Each barge provides a plurality of diagonally extending lift booms. Each boom is preferably pivotally supported upon the barge that it is connected to. Each lift boom has a lower end portion that attaches to the barge on a base and an upper end portion that includes a free end with a lifting end portion.
Lower connection members are provided for forming attachments between the barges and the platform to be lifted and salvaged or installed.
A supplemental lifting frame is provided that is connectable to the package to be lifted and salvaged or installed. The supplemental lifting frame includes receptacles that receive the free end portions of the booms during a lift.
The supplemental lifting frame can include horizontal beams and diagonal beams associated with each boom.
In the preferred embodiment, there are pairs of booms that align, each of said pairs being positioned respectively on opposite of the barges. For example, in the preferred embodiment, there are four booms on each barge, producing an overall four pair of aligned booms.
Horizontal load spreader surfaces can be placed on the barges and spaced generally on opposite sides of the package being lifted. These load spreader surfaces or base members are at the base of each boom and pivotally support the boom, spread the load to the barge structure as required and also provide sliding or horizontal adjustment of the base of some or all booms relative to the barge upon which they are supported.
The supplemental lifting frame preferably comprises horizontal beams that span between booms on opposite of the barges, diagonal booms that extend from an end portion of a horizontal beam to the lower end portion of the platform and a connection that joins the horizontal beams and diagonal beams with a pinned arrangement that disallows substantial bending moment in the horizontal beam and in the platform leg.
Each boom can be provided with a winch with a cable wound thereupon. The lower connections can include cables such as winch cables that span between the barges and the platform.
The present invention provides a method for the offshore salvage or installation of a fixed offshore platform. The method includes transporting a catamaran work platform to a desired site of the fixed offshore structure. The catamaran work platform including a pair of barge supported decks that are positioned at spaced apart and generally parallel positions relative to one another.
A lifting assembly is attached to the platform at multiple positions, including positions that are at least on generally opposite sides of the platform, and at upper and lower positions on the platform. The lifting assembly includes two opposed lifting booms, each connected by at least one lifting end portion to a frame that is attachable to the platform. The method further comprises pulling the two barge decks together.
In the method, the frame includes a horizontal beam that spans between the upper end portion of two aligned booms.
The method further comprises the step of subjecting the horizontal beams of the frame to compression only and little or no bending moment during the lift.
There are preferably two opposed lift barges as part of the method, each being a separate floating barge. However, a one piece barge construction could be provided that has separate spaced apart decks that carry the respective sets of lifting booms.
The lifting assembly can include a plurality of non-extensible diagonally extending lift booms, each removably connected at its ends to an end cap. dr
For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:
FIG. 1 is a perspective view of the preferred embodiment of the apparatus of the present invention;
FIG. 2 is a partial perspective view of the preferred embodiment of the apparatus of the present invention showing the connection made between the lower end portion of the leg of a platform to be removed or installed and the apparatus of the present invention;
FIG. 3 is a fragmentary, exploded, perspective view of the preferred embodiment of the apparatus of the present invention;
FIG. 4 is a fragmentary, sectional view of the preferred embodiment of the apparatus of the present invention illustrating the connection between horizontal and diagonal beam members;
FIG. 5 is a fragmentary frontal view of the preferred embodiment of the apparatus of the present invention showing the pin portion thereof;
FIG. 6 is another view of the pin portion of the preferred embodiment of the apparatus of the present invention;
FIG. 7 is an end view of the pin portion of the preferred embodiment of the apparatus of the present invention;
FIG. 8 is an end view of the retainer ring portion of the preferred embodiment of the apparatus of the present invention;
FIG. 9 is a fragmentary, perspective view of the preferred embodiment of the apparatus of the present invention illustrating the pin and retainer ring portions thereof;
FIG. 10 is a fragmentary, perspective view of the preferred embodiment of the apparatus of the present invention showing an end of one of the lifting booms;
FIG. 11 is a sectional view taken along lines 11xe2x80x9411 of FIG. 10; and
FIG. 12 is a partial, elevational view of the apparatus of the present invention.